If your dog is lethargic and shaking after vaccination, you’re likely feeling concerned and wondering whether these symptoms are normal or a sign of something serious. It’s not uncommon for dogs to experience some mild side effects after getting vaccinated.
Lethargy in dogs refers to extreme tiredness, low energy, or reluctance to move. Your dog may appear to be sleeping more than usual, less interested in playing, or slower in response to commands or attention.
Shaking or trembling in dogs can be due to a variety of reasons such as fear, pain, fever, or muscle fatigue.
When both shaking and lethargy occur after vaccination, these can be mild, temporary reactions—or signs of a more serious problem like a vaccine reaction.
We explain why dogs become lethargic and experience shaking after vaccinations, potential causes, when it’s normal, and when it’s time to worry.
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Dog Lethargic and Shaking After Grooming: What’s Happening?
A dog feeling lethargic and shaking after vaccination is usually experiencing mild, short-term side effects that are common after immunization. These symptoms can result from your dog’s immune system responding to the vaccine, which may cause temporary fatigue, muscle soreness, or low-grade fever—leading to shaking or shivering.
Some dogs may also feel stressed or anxious after the vet visit, which can add to the trembling.
While these signs typically resolve within 24 to 48 hours, persistent lethargy, severe shaking, vomiting, facial swelling, or difficulty breathing could indicate an allergic reaction or other serious issue and require immediate veterinary attention.
Dog Lethargic and Shaking After Grooming - Common Causes
1. Normal Immune Response to the Vaccine
One of the most common reasons for a dog being lethargic and shaking after vaccination is a mild immune system response.
Just like humans may feel tired or run down after receiving a vaccine, dogs can experience similar effects.
The body is working to build immunity.
This process can make your dog feel fatigued or weak.
Slight shaking may result from mild discomfort or fever.
This response usually resolves on its own within 24–48 hours. Your dog may simply need extra rest, water, and comfort.
Related: Dog lethargic and shaking after grooming (Here’s why)
2. Pain or Soreness at the Injection Site
If your dog is shaking and lethargic after vaccination, it might be due to pain or tenderness at the injection site.
Some dogs react strongly to the pain or inflammation where the shot was given.
They may guard the area, move slowly, or shiver due to muscle discomfort.
In some cases, a small lump or swelling may also form near the injection site.
Pain-related shaking usually resolves once the discomfort eases, typically within a day or two.
3. Fever as a Side Effect
Mild fever is another reason your dog may be lethargic and shaking after vaccination.
A fever occurs when the body reacts to the vaccine and raises its internal temperature to fight off what it perceives as a threat.
This can cause chills, tremors, and low energy.
While a low-grade fever isn’t unusual, it should pass quickly. If your dog continues to run a fever or worsens, contact your vet.
Related: Dog shaking and panting for no reason (Here’s why)
4. Vaccine Hypersensitivity or Allergic Reaction
In some rare cases, a dog may be lethargic and shaking after vaccination because of an allergic reaction or hypersensitivity to the vaccine components.
Symptoms may include:
Shaking and weakness
Swelling of the face or muzzle
Vomiting or diarrhea
Pale gums
Difficulty breathing
Collapsing or fainting
These signs often appear within minutes to a few hours of receiving the shot and require immediate veterinary attention.
This is a veterinary emergency, especially if the dog becomes non-responsive or has trouble breathing.
5. Stress or Anxiety After a Vet Visit
Sometimes, a dog being lethargic and shaking after vaccination has less to do with the shot itself and more to do with the experience of the vet visit.
Dogs can become highly stressed from car rides, the clinic environment, handling by strangers, or other animals.
This anxiety can linger after the visit and lead to trembling, pacing, or hiding.
Your dog might also be tired from the emotional toll of the event.
While this isn’t a medical reaction, it’s still important to observe your pet closely to make sure the symptoms are purely stress-related and not something more serious.
6. Multiple Vaccines Given at Once
Dogs who receive multiple vaccinations in one visit are more likely to show signs like being lethargic and shaking afterward.
The immune system has more to respond to, which can amplify the body’s reaction.
It’s also more taxing physically and may increase the risk of temporary side effects or discomfort.
Some vets space out vaccinations for smaller or more sensitive dogs to reduce the chances of stronger side effects.
7. Pre-existing Conditions
If your dog has an underlying health condition, they might react more intensely to a vaccination.
Dogs with autoimmune issues, metabolic disorders, or on medications may have a heightened sensitivity.
Older dogs or very young puppies can also be more vulnerable.
If your dog lethargic and shaking after vaccination seems more severe than expected, it could be due to their overall health status.
What to Watch For: Normal vs. Serious Symptoms
Here’s how to distinguish between normal vaccine side effects and signs that something’s wrong.
Normal Reactions (lasting less than 48 hours):
Mild lethargy
Slight shaking or trembling
Low-grade fever
Swollen or tender injection site
Reduced appetite
Temporary lack of energy
Concerning Reactions (seek immediate veterinary help):
Severe or prolonged shaking
Extreme lethargy (won’t get up, unresponsive)
Vomiting or diarrhea
Facial swelling or hives
Pale gums or collapse
Difficulty breathing
Symptoms lasting more than 48 hours or getting worse
What to Do If Your Dog Is Lethargic and Shaking After Vaccination
If your dog is showing mild signs of discomfort or lethargy:
Allow them to rest in a quiet, comfortable space.
Make sure they have access to fresh water and encourage hydration.
Monitor their temperature if possible (normal dog temperature: 101–102.5°F).
Avoid touching or pressing the injection site.
Offer bland food if they seem interested in eating.
If your dog is not improving within 48 hours, or symptoms worsen at any point, call your vet immediately. Dogs with allergic reactions may need antihistamines or emergency treatment.
How to Prevent or Minimize Side Effects
To reduce the chances of your dog being lethargic and shaking after vaccination, consider the following tips:
Talk to your vet: Discuss your dog’s health history and any previous vaccine reactions.
Space out vaccines: Particularly for small breeds or senior dogs.
Monitor closely after vaccination: Stay with your dog for several hours and watch for signs of distress.
Avoid overstimulation post-visit: Let them rest and recover quietly.
If your dog has had prior bad reactions, your vet may suggest pre-treatment with antihistamines or splitting vaccines over multiple visits.
Key Takeaway: Dog Lethargic and Shaking After Vaccination
A dog that is lethargic and shaking after vaccination is often experiencing a mild, temporary response to the vaccine. In many cases, this is completely normal and resolves within a day or two. However, persistent symptoms, worsening condition, or signs of an allergic reaction should never be ignored.
Pay close attention to how your dog behaves in the hours and days following vaccination. If you’re ever in doubt, don’t hesitate to contact your vet.
Vaccines are vital for your dog’s long-term health and safety. By being informed and vigilant, you can help ensure your dog recovers comfortably and safely after their shots.